Water meters generally have disc-shaped closures threadedly attached to the bottoms of their casings. The pressurized water within the casing imposes two radial forces on the casing wall. The first force occurs at the inner surface of the casing wall directly above the closure and is directed outwardly. The second force occurs at the wall immediately adjacent to the closure threads and is caused by forces on the upper surface of the closure that are transmitted through the closure at the lower thread surfaces. When standard screw threads are used, the lower force-transmitting surfaces of the closure threads face outwardly and cause the second radial force on the wall to be directed outwardly and additive to the first force. In such a structure thicker walls are needed to resist the sum of these radial burst forces.